Arboriculture & Urban Forestry 35(2): March 2009 lages. Overall, greenspaces in Milan covers a surface of 15.20 km2 (5.86 mi2 imately 11.60 m2 (124.86 ft2 Public greenspaces cover a surface of 1.13 km2 (0.44 mi2 3.4 m2 (36.60 ft2 ) with a population 316,000 inhabitants. ) with ); the average amount of greenspaces per capita is approx- ; Agenzia Mobilità e Ambiente, 2002). Bari (41°7’3”N; 8°32’55”E) extends to approximately 116.20 km2 (44.87 mi2 ) of greenspaces per capita (ISTAT, 2005). Bird Species Survey In each greenspace, we collected a number of data related to the richness and abundance of bird species. From March 2005 to July 2006, birds were observed and recorded during the breed- ing season by means of point-counts with unlimited distance (Bibby et al. 2000). “Point-counts” are a common method for sampling bird species (Bani et al. 2006) because it allows an extensive surveying of sample areas and the surrounding land- scape (Blondel et al. 1970; Reynolds 1990). In addition, this method enables collecting a wide range of ecological data on species with a cost-effective balance (Selmi and Boulinier 2003). In the study, birds were surveyed placing each sample within a grid of 250 m x 250 m while avoiding the overlapping of two continuous observations. Overall, 80 point-counts were covered during field campaigns. Among bird species surveyed in the two locations, two species were assumed as potential indicators of urban forest functionality: great tit (Parus major Linnaeus 1758) and the serin (Serinus serinus Linnaeus 1766). Both species were found in the two locations in more than 50 point-counts. Furthermore, great tit and serin are within the 15 target spe- cies described by the “atlas of birds” of Milan (Avium, 2006). Species abundance for the two indicator species was expressed in terms of number of individuals per point-count (Bibby et al. 2000). DATA ANALYSIS As first step, we performed a cluster analysis using UPGMA method (Unweighted Pair Group Method using arithmetic Aver- ages) which allowed comparing birds in terms of species com- position over the sixteen greenspaces (Spellerberg et al. 1999). In addition, we analyzed the structural and spatial char- acteristics of the sixteen urban greenspaces, such as: dimen- sion in hectares, percentage of vegetation cover, and distance from the core center of the city (identified by the center of the polygonal area representing the city – see Table 1). These data were analyzed using a nonparametric test: “R-Spearman Coefficient” (due to the non-normal distribution of observa- tions). Linear regression models were used to predict spe- cies richness on the basis of greenspaces’ characteristics. We measured the DBH [Diameter Breast Height, taken at 1.3 m (4.27 ft) above ground] of the closest 100 trees surrounding each point-count within a radius of 100 m (328 ft). DBH values were then analyzed in relation to species abundance values con- sidering the following intervals of DBH: minimum, first quartile, median, third quartile, and maximum. Such intervals were used to derive input data for an additional regression model. For each DBH interval, we compared the observed species abundance with the average abundance across the 80 point-counts and used those observations with higher values to construct an “optimal” model of the DBH distribution. All the other observations were instru- mental for creating a “minimal” model of this distribution. The “U-Mann-Whitney Test” was used for the scope. This approach 81 Table 1. Synthetic park’s features. Forest cover (the area covered by trees) correlation was not evaluated in Lama Balice park, because the natural vegetation was populated with shrubs and not trees. Urban forest area Milano Parco Nord Milano Trenno Milano Bosco in città Milano Sempione Milano Monte stella Milano Montanelli Parco Ravizza Milano Cave Parco Solari Milano Forlanini Parco Trotter di Turro Bari Umberto 1 Bari 2 giugno Bari Lama Balice Area (ha) MI1 MI2 MI3 MI4 MI5 MI6 MI7 MI8 MI9 Giardini Via Pallavicino MI11 Milano Lambro MI10 MI12 MI13 BA1 BA2 BA3 Code 596,5 61 49,8 51,2 38,6 19,4 7,8 119,1 5,6 59,7 6,2 71,7 13,1 1,8 4 119 Distance from the city 7168 6895 8800 1503 5256 1424 1812 7032 1951 5572 2396 5774 4306 0,1 2000 7500 Forest cover (ha) 80,117 46,71 38,628 26,912 15,858 10,54 3,284 37,042 2,122 31,834 2,352 38,539 6,967 0,27 1 N.A. has been used in previous studies (Massa et al. 2003a) and it fol- lows the assumptions that: an high level of abundance is gener- ally preferable for birds in urban settings (Bock and Jones 2004); that birds select forest with high values of DBH, mature urban forest; and that species in urban environments are likely to occur within heterogeneous and uneven-aged forest vegetation (Blair 1996; Donnelly and Marzluff 2006; Sandström et al. 2006). RESULTS Table 2 illustrates bird species diversity for each of the ana- lyzed urban greenspaces. In total, 56 species were record- ed: 53 species in Milan and 11 in Bari; and 4,393 speci- mens were indentified: 3,587 in Milan and 649 in Bari. The large part of these species are typical of forest-type habitat (Keast 1990; Hinsley et al. 1995; Massa et al. 2003b; Bani et al. 2006), such as: “wren” (Troglodytes troglodytes L.); “wryneck” (Jynx torquilla L.); “short-toed treecreeper” (Certhia brachy- dactyla C.L.Brehm 1820); “golden oriole” (Oriolus oriolus L.); “jay” (Garrulus glandarius L.); and “great spotted woodpecker” (Dendrocopos major L.). Other species are common in farm- Table 2. Number of bird species identified and number of specimens detected in each greenspace. Green spaces Milano Parco Nord Milano Trenno Milano Bosco in città Milano Sempione Milano Monte stella Milano Montanelli Parco Ravizza Milano Cave Parco Solari Milano Forlanini Parco Trotter di Turro Bari Umberto 1 Bari 2 giugno Bari Lama Balice Code MI1 MI2 MI3 MI4 MI5 MI6 MI7 MI8 MI9 Giardini Via Pallavicino MI11 Milano Lambro MI10 MI12 MI13 BA1 BA2 BA3 N of species 38 18 32 19 19 12 6 34 12 22 10 26 8 8 11 16 N° of specimens 1378 193 244 397 206 75 40 379 78 276 39 227 55 402 125 122 ©2009 International Society of Arboriculture
March 2009
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